The present invention relates to a technology effectively applicable to a light control circuit capable of controlling the luminance of the backlight of a display panel. Further, it relates to a technology effectively applicable to, for example, a semiconductor integrated circuit for controlling the backlight of a display unit using a transmissive or semi-transmissive liquid crystal display panel or a liquid-crystal-display control drive device constructed as a semiconductor integrated circuit, that drives a liquid crystal display panel.
As a display unit for portable electronic equipment such as cellular phones and PDAs (Personal Digital Assistants), transmissive or semi-transmissive liquid crystal display panels having a backlight on their rear face have been used in these years. Such equipment is mounted in it with a display control unit (liquid crystal controller) constructed as a semiconductor integrated circuit, that controls display in the liquid crystal display panel, a driver that drives the liquid crystal display panel, a driver that drives the backlight, and a controller that controls the luminance of the backlight.
It is known that the viewability of the display in a liquid crystal display panel is caused to greatly fluctuate by ambient brightness. Portable electronic equipment such as cellular phones is used in environments largely different in ambient brightness, for example, indoors and outdoors. Therefore, the brightness of the backlight of a transmissive or semi-transmissive liquid crystal display panel used in these equipment is adjusted according to ambient brightness in some cases. Examples of invention associated with the adjustment of the brightness of the backlight of a liquid crystal display panel include that disclosed in Japanese Unexamined Patent Publication No. Hei 9 (1997)-146073.